In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.
Conventional tool cartridges, particularly ISO tool cartridges, for finish operations have a tool cartridge with a screw to bear against a cutting insert to hold it in a desired seated position for machining operations. FIG. 1A shows an example of a conventional, “screw down” tool cartridge 10. In the conventional tool cartridge 10, radial adjustment, i.e., in the Y-axis direction in FIG. 1A, is performed by a socket set screw (not shown) positioned in threaded opening 12 (threaded opening 12 is illustrated in cut-away view for ease of viewing). On one end of the screw there is a driving hex hole to engage with a wrench having a suitable mating shape, as is conventional. The other end of the screw has, depending on the quality of the tooling cartridge, a polished ball or oval surface (in high end designs) or a simple flat surface (in inexpensive versions).
The conventional tool cartridge 10 has a body 14 that represents an essentially ridged structure. In use and to raise a vertex 16 of the cutting insert 18, one of two possibilities have to be executed: 1) a clamping screw has to be loosen, an adjustment performed, a clamp screw tighten, the adjustment should be checked and any correction made before the process is completed; or 2) a clamping screw has to be pre-tightened arbitrarily to allow the clamping screw to stretch enough to provide an adjustment range. Both methods 1) and 2) are criticized by typical machinists on the shop floor.
Another problem of the conventional design is a negative gain of resolution. FIG. 1B shows a line drawing of the conventional tool cartridge 10 from FIG. 1A. In FIG. 1B, a typical axial location of the threaded opening 12 for an adjustment screw is illustrated. The conventional tool cartridge 10 shown has a ratio of an adjustment screw distance (L1) to a vertex cutting edge distance (L2) of about 1:1.5. This means that a small radial movement of the adjustment screw in the threaded opening 12 will be amplified 1.5 times on the cutting edge located at the vertex 16. For reference, the axial direction is the X-axis direction in FIGS. 1A and 1B.
A further problem of the conventional design is a high expansion stress of the clamping screw 20, which is stretched by adjustment, and the high compression stress of the adjustment screw, which is trying to bend the rigid structure of cartridge body 14. Neither stress state is ideal.
U.S. Pat. No. 5,066,173 describes a boring bar in which a slot with a recess is introduced into the boring bar to allow the front of the cartridge to be flexible enough to reduce the stress on the clamping screw as well as on the adjustment screw. However, the disadvantage of this design is the low resolution of adjustment as it depends solely on the thread pitch of the screw and the adjustment screw resides in the cutter body (and not within the cartridge itself).
U.S. Pat. No. 7,753,626 discloses a cartridge that has a differential screw mechanism. However, the cartridge does not address the cantilever problem and the clamping screw problem discussed above.